Delay Right Channel of Stereo Audio in FFmpeg

This article explains how to delay only the right channel of a stereo audio file using FFmpeg. You will learn the exact command-line syntax and filters required to apply a precise time delay to the right channel while leaving the left channel untouched, resulting in a modified stereo output file.

To delay only the right channel of a stereo audio file, you can use FFmpeg’s built-in adelay filter. This filter allows you to specify distinct delay times for each individual audio channel, separated by a pipe (|) character.

The Basic Command

To delay the right channel by a specific number of milliseconds, use the following command structure:

ffmpeg -i input.mp3 -af "adelay=0|500" output.mp3

How It Works

• -i input.mp3: Specifies the input audio file.
• -af: Applies an audio filter.
• "adelay=0|500": This is the delay filter argument.
  • The first value (0) represents the delay for the first channel (Left) in milliseconds.
  • The second value (500) represents the delay for the second channel (Right) in milliseconds.
• output.mp3: The name of the resulting output file.

Delaying by Samples

If you require sample-accurate delays instead of milliseconds, you can append an S to the delay values. For example, to delay the right channel by 22,050 samples:

ffmpeg -i input.wav -af "adelay=0|22050S" output.wav

Applying to Video Files

If your audio is part of a video file and you want to delay the right audio channel while copying the video stream without re-encoding it, use this command:

ffmpeg -i input.mp4 -af "adelay=0|500" -c:v copy output.mp4